Chlamydia trachomatis

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Scientific classification
Genus: Chlamydia Species: Trachomatis

Description and significance

Chlamydia trachomatis is a pathogen that causes many serious health threats to humans. Chlamydia is one of the most common STD which is caused by Chlamydia trachomatis. An estimated 4 million C. trachomatis infections occur annually among the sexually active population in the United States. The majority of persons with C. trachomatis infection are not aware of their infection because they do not have symptoms. The infection is easily cured if diagnosed, but many infections remain untreated and lead to other illnesses such as infertility in both men and women. Another disease caused by C. trachomatis is trachoma, most common cause of blindness among children in Africa and other developing nations.

Genome structure

The genome of Chlamydia trachomatis contains 1,042,519 base pairs of DNA encoding 938 genes. C. trachomatis strains have an extrachromosomal plasmid, which was sequenced to be a 7493-base pair plasmid.

Cell structure and metabolism

Chlamydia trachomatis is structurally gram negative and is one of three bacterial species in the genus Chlamydia. It was once thought to be a virus because it could have not been cultured in an artificial medium. C. trachomatis is an obligate intracellular pathogen that lives within human cells and cannot make its own ATP. This means that they are unable to replicate outside of a host cell. The pathogens have evolved a unique biphasic life cycle. They alternate between two functionally and morphologically distinct forms; elementary body and reticular body. Elementary body (EB) is infectious, but metabolically inert (chemically inactive). EB is taken up by host cells, primarily byreceptor-mediated endocytosis. the bacteria prevent fusion of the endosome and lysosome, but the mechanism of this is not known. Inside the endosome, the EB differentiates into a metabolically active but non-infectious form, reticulate body (RB) using energy sources and amino acids from the host cell. RB replicates and ultimately forms new EBs that are capable of infecting additional cells.

Ecology

Chlamydia trachomatis is a pathogenic bacteria. It cannot survive outside of a eukaryotic host cell. Humans are the only known host for C. trachomatis. It is transmitted by sexual contact with an infected individual.

Pathology

Chlamydia trachomatis infection is usually spread by sexual intercourse and can cause numerous diseases in both men and women. Both sexes can display urethritis (an inflammation of the urethra), proctitis (rectal disease and bleeding.) In men, the infection can cause prostatitis (an inflammation of the prostate gland) and epididyitis (an inflammation of the epididymis, which is a long, tightly coiled tube that lies above and behind each testicle.) In women, pelvic inflammatory disease (PID) is very common. This causes scarring of the uterus and fallopian tubes and often results in infertility. Ectopic pregnancy (fetus develops outside the womb), and acute or chronic pelvic pain are also frequent complications caused by C. trachomatis. Occasionally, C. trachomatis can spread from the genital area and affect the liver and joints. It is also an important neonatal pathogen, where it can lead to infection of the eye and pulmonary complications. Trachoma is a communicable disease that may lead to considerable visual disability. It infects 150 million people and 6 million people are blinded in developing countries. Organisms are transmitted from eye to eye by flies and through hand-to-eye contact in endemic areas. The initial infection is in the thin lining over the eye, the conjunctiva, and the upper eyelids resulting in a chronic inflammation that spreads to the corneas, eventually leading to scarring. Over a period of years, the scars may eventually cause eyelashes to point inwards, scratching the cornea of the eye and in many cases causing irreversible blindness.

References

Eley, Adrian. 2003. Chlamydia trachomatis is bad for your sperm! Microbiology Today, 30: 61-62

http://www.news-medical.net/?id=1029

Kalman, Sue et al. 1999. "Comparative genomes of Chlamydia pnuemoniae and C.trachomatis." Nature, 21: 385-389.